A short bash script to simulate a coinflip.

flip.sh

#!/bin/bash
FLIP=$(($(($RANDOM%10))%2))
if [ $FLIP -eq 1 ];then
    echo "heads"
else
    echo "tails"
fi

Also to simply the conditional syntax by chaining boolean logic, and removing redundant syntax you can get it pretty clean:

#!/bin/bash
(( RANDOM % 2 )) && echo "heads" || echo "tails"

@srozanc-mcs ah, that works because the value returned by (()) is also the return code! (That must also be why the set option to bail on any error may unexpectedly bail on a line that includes (()), depending on the result.)